[Octave-bug-tracker] [bug #53909] localtime() does not access TZ on windows

[Ian McCallion]

URL:
  <http://savannah.gnu.org/bugs/?53909>

                 Summary: localtime() does not access TZ on windows
                 Project: GNU Octave
            Submitted by: ianmcc
            Submitted on: Tue 15 May 2018 12:14:24 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.4.0
        Operating System: Microsoft Windows

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Details:

This script should produce different values for t1, t2 and t3 because they
should be representing the current time in three different timezones (unless
you are already in CST of course):

     x = time ();
     t1 = localtime (x)
     setenv TZ UTC0
     t2 = localtime (x)
     setenv TZ CST6CDT
     t3 = localtime (x)
     unsetenv TZ


The script works on unix versions of Octave, but at least on Octave Windows
4.2.2 and 4.4.0, after running this t1==t2==t3=

    usec =  140346
    sec =  41
    min =  35
    hour =  8
    mday =  12
    mon =  4
    year =  118
    wday =  6
    yday =  131
    isdst =  1
    gmtoff = 0
    zone = GMT Daylight Time


This next script however DOES produce correct values for t1, t2 and t3.

     x = time ();
     t1 = localtime (x)
     setenv TZ UTC0
     mktime(localtime(1)); % Force Octave to access the TZ environment
variable
     t2 = localtime (x)
     setenv TZ CST6CDT
     mktime(localtime(1)); % Force Octave to access the TZ environment
variable
     t3 = localtime (x)
     unsetenv TZ
     mktime(localtime(1)); % Force Octave to access the TZ environment
variable


The reason this works and the first script didn't is probably a bug that the
posix layer shipped with windows versions of Octave where tzset() is not
called by localtime() and possible other timezone-dependent functions. If
necessary (i.e. can't fix the posix layer) it should be fixed in Octave, by
explicitly calling tzset wherever it may be needed.




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